This invention relates to a clutch system of the friction type placed in a power transmission system. Typical clutch systems include a clutch input such as a clutch basket, a clutch output such as a center clutch, and one or more plates making up a clutch pack and disposed between the clutch input and clutch output. When the clutch pack is compressed, the clutch input and clutch output become rotationally coupled.
Most motorcycles incorporate a manual transmission coupled to the engine via a multi-plate clutch assembly. Typically, the multi-plate clutch is engaged/disengaged by the driver via a lever mounted on the handlebar. Although the lever operated clutch allows the driver to control the clutch engagement/disengagement, often the motorcycle driver finds the clutch lever difficult to operate smoothly. New riders have difficulty adjusting to smoothly engaging the clutch while operating the throttle to move the vehicle from a standing start. Experienced riders may need to partially disengage the clutch when traveling slowly to allow the engine to continue running without stalling. Motorcycle racers often have a difficult time controlling the engagement of the clutch and the application of the throttle to maximize acceleration. Off-road motorcycle racers often need to stop the rear wheel suddenly with the rear brake, causing the engine to stall if the clutch is not first disengaged. An automatic clutch can help overcome many of the problems associated with a manual clutch.
In other situations, a torque-sensitive clutch may be beneficial to the operator. When racing, a vehicle may approach a corner at high speed. To negotiate the corner quickly, the driver must simultaneously brake and down shift the transmission to the appropriate gear to exit the corner with maximum acceleration. If the operator downshifts the transmission too quickly, the drive wheels of the vehicle will increase the engine speed and cause braking forces which may cause the driving wheels to loose traction. In this situation, it is desirable to have a clutch system that will allow the clutch to slip when the torque in the clutch is reversed from acceleration to deceleration.
Experienced motorcycle riders desire to have the capabilities of a dynamically actuated clutch, such as an automatic centrifugal clutch or a torque sensitive clutch but still want complete control of the clutch engagement/disengagement via a manually operated clutch disengagement lever. Existing dynamic clutch systems that incorporate a manual clutch disengagement lever suffer from a clutch lever whose operation and or feel changes as the dynamic engagement mechanism changes. For example, clutches that incorporate a centrifugal mechanism may require very little effort at low RPMs to overcome the centrifugal mechanism to disengage the clutch and more effort at high RPMs. Clutches that incorporate a torque-sensitive mechanism typically have a reduced clutch lever effort during deceleration. For experienced riders, the change in clutch lever “feel” is undesirable. The present invention seeks primarily to overcome the limitation of the change in “feel” of the clutch lever in a clutch system incorporating dynamic engagement mechanisms by isolating the dynamic engagement portion of the clutch system from the manual disengagement system. The present invention also seeks to fit in the space occupied by a typical clutch system.